These seem to be the current run of “How Not to Be a Jerk on the Trains” posters. This one reads: There are people who can be helped by your kindness – give up your seat with a smile.

There are four-six seats on each train car reserved for those in need – the elderly, pregnant women, injured folk, etc. Of course, if they’re not using them, others are free to (this is occasionally up for debate).